We present a new detailed abundance study of field red horizontal branch ( RHB ) and blue horizontal branch ( BHB ) non-variable stars .
High resolution and high S/N echelle spectra of 11 RHB and 12 BHB were obtained with the McDonald 2.7 m telescope , and the RHB sample was augmented by reanalysis of spectra of 25 stars from a recent survey .
We derived stellar atmospheric parameters based on spectroscopic constraints , and computed relative abundance ratios for 24 species of 19 elements .
The species include Si ii and Ca ii , which have not been previously studied in RHB and BHB ( T _ { eff } < 9000 K ) stars .
The abundance ratios are generally consistent with those of similar-metallicity field stars in different evolutionary stages .
We estimated the masses of the RHB and BHB stars by comparing their T _ { eff } - log g positions with HB model evolutionary tracks .
The mass distribution suggests that our program stars possess masses of \sim 0.5 ~ { } M _ { \sun } .
Finally , we compared the temperature distributions of field RHB and BHB stars with field RR Lyraes in the metallicity range -0.8 \gtrsim [ Fe/H ] \gtrsim - 2.5 .
This yielded effective temperatures estimates of 5900 K and 7400 K for the red and blue edges of the RR Lyrae instability strip .